The problem of microbial contamination of water systems has become a major concern particularly in rural areas. The vast distribution network needed to service areas of low population density, as well as the high cost for the construction of large water treatment plants, makes these methods for resolving the problem both economically and structurally infeasible. In rural areas the microbial contamination of well water, from cess-pools and animal fecal contamination, represent a serious problem.
Another area wherein microbial contamination is a problem is in residential swimming pools. The control systems utilized in these applications usually involves the use of microbiocide release agents at very high concentrations. The major concern in this area of application is the inadequacy of control over the use of such microbiocides and the resultant problems associated with their misuse.
Various methods are known which attempt to provide a solution to the problem of purifying microbially contaminated water. The major approach to the problem has been to provide a means by which controlled amounts of a microbiocide are added to the water system. However, the microbiocide concentration needed in such systems must be sufficiently high to effect rapid microbial kill but must also be low enough to be safe for human consumption. Such microbiocidal systems usually require holding tanks, to increase the residence time, in order to achieve sufficient microbial kill at physiologically safe levels of microbiocide release.
The concept of using silver impregnated carbon systems for water purification is also known. These systems function via sustained release of the silver into the contaminated water. Since high concentrations of silver are needed to rapidly kill the bacteria, a scavenger system must be utilized which will lower the silver concentration to physiologically safe levels. Alternatively, if lower silver concentrations are released into the contaminated water then holding tanks must be utilized to produce a high enough percentage kill of the bacteria to be physiologically acceptable.
It is also known that anion exchange resins can be utilized to separate various bacteria. This work has been reported by S. Daniels and L. Kempe in Chemical Engineering Progress Symposium Series vol. 62(69) pp 142-8 (1966).
The Japanese patent 74 80,241 granted Aug. 2, 1974 to Y. Fujiwara and O. Yagi describes the use of strong acid cation exchange resins, impregnated with bactericidal quaternary ammonium cations, for removing bacteria from contaminated water.
The U.S. Pat. Nos. 3,923,665 granted Dec. 2, 1975 and 3,817,860 granted June 18, 1974 both to J. Lambert and L. Fina, and 3,462,363 granted Aug. 19, 1969 to J. Mills disclose the polyhalide form of strong base resins having gel structures and their use in the purification of bacterially contaminated water. J. Woodward and M. Korczynski reported in Developments in Industrial Microbiology vol. 14 pp. 361-369 (1973) that these resins tended to leach iodine during use and that an additional activated charcoal bed was needed to obtain no iodine residuals.